题解 | #链表内指定区间反转#

# class ListNode:
#     def __init__(self, x):
#         self.val = x
#         self.next = None
#
# 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
#
# 
# @param head ListNode类 
# @param m int整型 
# @param n int整型 
# @return ListNode类
#
class Solution:
    def reverseBetween(self , head: ListNode, m: int, n: int) -> ListNode:
        dummy = ListNode(-1)
        dummy.next = head
        a, d = dummy, dummy
        for _ in range(m - 1):
            a = a.next
        b = a.next
        for _ in range(n):
            d = d.next
        c = d.next
        pre = b 
        cur = b.next
        while cur != c:
            tmp = cur.next
            cur.next = pre
            pre = cur
            cur = tmp
        a.next = d
        b.next = c 
        return dummy.next
        
最后返回的不能是head，必须要返回dummy.next 不一样的

解法链接